If nothing else, San Jose’s 3-0 home loss to the Chicago Fire on Wednesday should serve as a great PSA to their fan base: If you’re going to ride on the Quakes Playoff Bandwagon, please fasten all safety belts. The trip could get very bumpy, very quickly.

Coming in 13 points out of the final playoff spot and with four teams to pass, Chicago was supposed to be just a speed bump for the surging Quakes.

Instead, after being unable to crack the Fire’s youthful back line in the first 35 minutes, San Jose seemed to lose their way, eventually suffering their first home defeat since July 31.

“A lot of guys said it when we came in (before the game), that we’ve got to keep our foot on the gas,” Quakes center back Brandon McDonald said. “We’re not guaranteed to be in the playoffs yet.”

That elusive first postseason berth since reinstatement in 2008 got a little further away Wednesday. The Quakes (11-8-6) dropped to eighth place as Colorado (11-7-8) , 4-1 victors against Philadelphia, moved up to sixth and Seattle slid by on San Jose’s suddenly worsened goal differential.

“We said from the beginning, preparing for this game – it doesn’t matter about their record, it doesn’t matter that they probably won’t make the playoffs,” Quakes goalkeeper Jon Busch said. “Unfortunately, I think we were a little casual tonight.”

San Jose came out looking to build on their 3-2 win in Toronto on Saturday, a game in which they flashed some of their most cohesive offensive play of the season. A number of early half-chances culminated in a free back-post header for Chris Wondolowski in the 23rd minute.

The ball was stopped short of the goal by the hand of rookie Fire defender Kwame Watson-Siriboe, but referee Abiodun Okulaja ruled the contact incidental, and despite a demonstrative response from the fiery Wondolowski, the Quakes never really regained their focus.

“The hand ball, that’s a game-changer, if we get the PK,” McDonald said. “But we can’t dwell on that. We’ve got to keep playing for 90 minutes.”

Wondolowski disagreed with the notion that the Quakes were looking too far ahead after a 5-1-1 stretch put them in good shape with regards to the league table.

“We kept the same mentality,” Wondolowski said. “We’re all a pretty loose group. It’s part of our character, and I think that’s one of the reasons why we have done well, is that we don’t get uptight. It might have looked like that because we were lacking in that final third at times.”

Nevertheless, coach Frank Yallop said he could tell from early on that his starting XI – unchanged from the Toronto match – was not gelling in the same manner on Wednesday.

“After 10 minutes, I was like, ‘This is not a good performance by us. We’ll be lucky to get out with a draw,’ ” Yallop said. “Once we got scored on, we didn’t really look like we were going to get back in the game. So it was a little disappointing.”

On the one hand, the Quakes won’t have long to wait to try to wash away the taste of defeat. San Jose travel Thursday to Columbus for a Saturday match against the Crew.

On the other hand, it’s a third match in eight days, with Yallop’s preferred XI having started both of the first two games. And San Jose aren’t talented enough to get results in Ohio unless they’re outworking the opposition.

“Hopefully it’s a wake-up call,” Busch said. “We were feeling good about ourselves, coming off a good win up in Toronto and the team’s playing well. And sometimes you do need a wake-up call that you can’t just show up every game and get a result.

“Any team in this league is capable of beating anybody. It doesn’t matter about the table, where teams are in the table. If you don’t show up and put 100 percent effort in, things like that happen.”

Geoff Lepper covers the Earthquakes for MLSsoccer.com. He can be reached at sanjosequakes@gmail.com . On Twitter: @sjquakes